Process for the preparation of



Patented Apr. 21, 1953 I 1 UNITED STATES PATENT OFFICE PROCESS FOR THEPREPARATION OF 11- AND fi-G-METHYL-IONONES- Heinrich Griitter,BrouggQSwitzerIand, assignor to Firmenich & 00., successeurs de laSoci't Anonyme M. Naef & Cie, Geneva, Switzerland, a corporation ofSwitzerland No Drawing. Application January 5, 1951, Serial. No.204,693. In SwitzerlandJanuary 18, 1950 8 Claims. (01. 260-587) 1 2: Thepresent invention has the object of providwith good yields particularlyunder the influence ing a process for the preparation of aand 13-6- ofacidic cyclization agents, this is to say of submethyl-ionones. stanceswhichwhen admixed solely to water, form This process is characterized inthat 5-methylliquids the pH value of which is lower than 5.2-isopropy1-1,5,7-decatrienone-9 is subjected to 5 Amongst thesecyclization agents, sulphuric acid a cyclization which yields conjointlystereo- (-60%), phosphoric acid (-83%) and boron triisomeric6-methyl-a-ionones and 6-methyl-fifluoride give the best results. Theconcentration ionones. of the. sulphuric acid may be between 58 to 62%The 5-methyl-2-isopropyl-1,5,7-decatrienone-9, (density 1.49 to 1.53),and the phosphoric acid I Eb.0.03 mm. 110-115; (1 :0394; n 2 =1.5225 10may be of 80 to 87% concentration (density becan easily be synthesizedby standard methods, tween 1.65 and. 1.7). r such as described inHelvetica Chimica Acta 30, The ketoneof the Formula III (which isliquid) 1812 (1947), 32, 1354 (1949) and 33, 2019 (1950)., can exist in.four different stereoisomeric forms in which the starting materialdimethylheptenone owing to its double bonds at the carbon atoms 5 isexchanged for 2-isopropyl-hexene-l-one-5 and 7.. The commercial productobtained by (Formula II), a product obtainable without difsynthesis is,however, a mixture in which one of ficulty from thujone, for example,according to the isomers may be more or less predominant Wallach(Annalen 275, 174 (1893), Berichte 30, according to the boiling point ofthe fraction 440 (1897), Simonsen, The Terpenes,"vol. 11, page utilized.The cyclization of this mixture yields 37, Second Edition). the aand5-6-methylionones which are, in turn,

It will now be indicated diagrammatically how mixtures of stereoisomers.The relative proporthis starting ketone can be prepared and how by tionsof the latter depend on the stereoisomerism cyclization it yieldsconjointly the aand 8-6- of the starting ketone but it is also possiblethat methyl-ionones (Formulae IV and V, respecthey are influencedatleast partly, by the conditively): tions in which the cyclization iscarried out.

CH3 CH3 0% CH3 CH3 CH3 CH1 CH2 C CH2 10 CH 0112 9 CH; 0 C o on (5H a EIzCO-OH3 3:11, i so Cfi cn Ca CH s GHa.

I II III 1 CH3 CH3 CH3 CH3 on, 0 CH 0113 C on" ofi o \CH "ofi o on H. tto te. t o

0% \CH3 \CH3 cfiz CHa CHa IV v Nothin could make one expect hithertothat The direct product of the process according to a substance like theketone of the Formula III the invention is a mixture of stereoisomers ofthe would cyclize according to the above scheme. In G-methyI-a-iononeand of the G-methyI-fl-ionone. fact, contrary to all known examples(cyclization 60 It does not difier or differs but little as regards ofpseudo-ionone, pseudo-irone, etc.), the 1' carits properties from theone obtained by the procbon atom which takes part directly in thecyclizaess described in U. S. patent application Serial tion of theprocess according to the invention is No. 778,752 of October 9, 1947.The stereoisonot adjacent to a double bond. In spite of this, mers ofeither the fi-methyl-a-ionone or of the the ketone of the Formula IIIcyclizes readily and G-methyl-B-ionone can be isolated from this di.

rect product as described in the said U. S. patent application.

This product, as well as the isolated 6-methy1- ionones can be utilizedin the perfumery and in the cosmetics industry, wherever a particularlyfine violet or orris root fragrance is desired.

Owing to the fact that the -methyl-2-isopropyl-1,5,7-decatrienone-9(Formula III) used as a starting material can be readily synthesized,the process according to the present invention has a marked advantageover the one that consists in the cyclization of the-methyl-pseudoionone, since the synthesis of the iro e is thus found tobe shortened and simplified.

It will now be described how the process according to the presentinvention can be carried out in practice:

Example 1 (phosphoric acid used as a cyclization agent) tween 00 and 110C. under 0.2 mm. Hg) are introduced at such a rate that the temperaturedoes not exceed 0 C. The solution is maintained subsequently at 0 C. for20 minutes, then heated to between and C, and maintained 15 more minutesat this temperature. It is mechanically agitated during the whole periodof the operation. It is then poured on ice, extract- Prior topurification, the irone has often a lower density (d4 minimum=0.930).

This product is a mixture of various stereoisomers of the airone typeand of a few of the fl-irone. The phenyl semi-carbazone melts at 172 0.,its 2,4-dinitrophenyl hydrazone at 120 C. These two derivatives areidentical with those yielded by the a-lIOIlB. In the mother liquors,stereoisomers may be found.

Example 2 (boron trifluoride used as cyclization agent) Into a solutionof 15.3 g. of 5-methyl-2-iso-" propyl-1,5,7-decatrienone-9 in 90 cc. ofdry benzene cooled to 0 C., a rather rapid flow of BF: is introducedduring about 30 minutes while stirring. The reaction manifests itself bya sudden Number increase in temperature which rises to 6-7 C.

The absorption of the boron trifiuoride then ceases: amount absorbed 6.3g. The irone-BFs complex is decomposed by means of 75 cc. of an 8% NaOHsolution. The layers formed are separated, washed with 15 cc. of a 25%NaOH solution (while stirring for 1 hour), dried, concentrated anddistilled. One obtains 11.7 g. of irone boiling at 83-87 C. under 0.15mm. Hg. Its constants are:

This is a mixture of divers stereoisomers of the a-irone type and of afew of the B-irone. The phenyl semi-carbazone has a melting point of 172C. which does not show any depression when mixed with that of theExample 1. One part melts below 159 C. and corresponds to difierentstereoisomers.

Instead of submitting to the cyclization mixtures of the variousstereoisomers of the 5- methyl-Z-isopropyl-1,5,7-decatrienone-9, thesaid various stereoisomers may be first enriched by fractionaldistillation, and the different fractions then subjected separately to acyclization producing mixtures containing different quantities of thestereoisomeric G-methyl-alpha-ionones and G-methyl-beta-ionones.

What I claim is:

1. A process for the preparation of aand fl-G-methyl-ionones,characterized in that 5- methyl-2-isopropyl-1,5,7-decatrienone-9 issubjected to a cyclization by action of an acidic medium which yieldsconjointly stereoisomeric fi-methyl-a-ionones and S-methyl-fl-ionones.

2. A process according to claim 1, in which the acidic medium is amedium which if dissolved in nine parts of water would give a 10%solution with a pH less than or equal to 5.

3. A process according to claim 2, characterized in that the said agentis sulphuric acid.

4. A process according to claim 2, characterized in that the said agentis phosphoric acid.

5. A process according to claim 2, characterized in that the said agentis boron trifluoride.

, 6. A process according to claim 3, characterized in that the saidagent is sulphuric acid of a density between 1.49 and 1.53 (58-62%) -'7.A process according to claim 4, characterized in that the said agent isphosphoric acid of a .the stereoisomeric 5-1nethyl-2-isopropyl-1,5,7-decatrienones-Q to be cyclised or selected accord- ,ing to boiling pointand then subjected to a cyclization yielding a mixture of stereoisomeric6-methyl-a-ionones and G-methyl-B-ionones.

HEINRICH GRIITTTER.

References Cited in the file of this patent UNITED STATES PATENTS NameDate 2,517,800 Naves Aug. 8, 1950 FOREIGN PATENTS Number Country Date262,269 Switzerland Oct. 1, 1949 Simonsen, The Terpenesfif vol. II, pp.37 and 38, 2d ed., pub. 1949 by Cambridge University Press.

1. A PROCESS OF THE PREPARATION OF A- AND B-6-METHYL-IONOSES,CHARACTERIZED IN THAT 5METHYL-2-ISOPROPYL-1,5-7-DECATRIENON-9 ISSUBJECTED TO A CYCLIZATION BY ACTION OF AN ACIDIC MEDIUM WHICH YIELDSCONJOINTLY STEREOISOMERIC 6-METHYL-A-IONONES AND 6-METHYL-B-IONONES.